Catalysts of Organic and Inorganic Origin. 299 



Oxidation of Hydroquinone by Potassium Ferricyanide and Hydrogen 



Peroxide. 









Concentration 



of variant substance (per cent.). 







1. 



0-5. 



0-25. 



o-i. 



0-05. 



o-oi. 



-005. 



-ooi. 



o -oooi. 



Experiment A . . . 



17 

 (17) 



20 

 (10) 



23 

 (5 -6) 



32 

 (3 -2) 



38 

 (0 -76) 



48 

 (0 -48) 



56 

 (0 -24) 



2378 

 (2 -38) 



Trace 

 only 



Experiment B ... 



nil 



(17) 



22 

 (11) 



38 

 (9-5) 



66 

 (6 -6) 



Incom- 

 plete 

 after 



3 days 



Faint 

 after 

 1 week 



Trace 

 only 







Experiment C ... 



17 

 (17) 



21 

 (10 o) 



32 

 (8) 



1740 

 (174) 



Incom- 

 plete 

 after 



1 week 



Faint 

 after 

 1 week 



Trace 

 only 







The experiments show that in the presence of abundance of hydrogen 

 peroxide an oxidase action is perceptible down to a concentration of 

 O'OOl per cent, of potassium ferricyanide (1 grm. in 100,000 c.c. of water), 

 and that the relative oxidase activity increases with dilution down to a 

 concentration of O'OOo per cent., beyond which it rapidly decreases to nil. 

 the limit being possibly set by extreme conditions of mass action. 



Apple Oxidase. 



In regard to the influence of KI, KC1, KBr, KF, in all cases the fluoride 

 acted more or less strongly as an antioxidase, while the other salts for the 

 most part exercised a slight retarding influence in the order given, although 

 this was imperceptible with the guaiacum test. The chloride feebly and the 

 bromide more strongly accelerated the decomposition of H 2 2 , and also the 

 oxidation of hydroquinone in the presence of H2O2. 



When in excess, all four salts strongly retard or even prevent the browning 

 of pounded apple pulp, but without destroying the oxidase. On washing 

 away the excess of the salts and adding H 2 2 , a blue is given with guaiacum 

 and the KBr pulp turns rapidly, the KC1 pulp slowly, and the KF pulp very 

 slowly brown. Pulp pounded witb 2-per-cent. barium chloride remains 

 colourless, and after three hours, on adding dilute H2O2, a feeble evolution of 

 gas is shown and the pulp browns rapidly, but not if previously boiled. If 

 the pulp is washed with water, filtered, and the residue pounded up with a 

 little fresh water, it is able to actively decompose H 2 2 , gives a distinct blue 

 with guaiacum, and on exposure to air slowly browns. Barium chloride, 

 therefore, does not destroy the oxidase but acts as an antagoniser, and 



vol. lxxxviii. — b. z 



